Image Synthesis using Adjoint Photons. Motivation Participating Media Simplify Importance Sampling Support Wavelength Dependence.

Image Synthesis using Adjoint Photons

Motivation

• Participating Media

• Simplify Importance Sampling

• Support Wavelength Dependence

Participating Media

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Ray Marching Result

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Media as Probabilistic Entity

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Probabilistic Media Example

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Probabilistic Media Example 2

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Rendering Comparison

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Traversal Comparison

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Software Impact

• Probabilistic media act like surfaces– Subclass them from Surface

• No volume pass after surface shading

• Separates intersection and shading

Shading Kernels

• Surfaces:

• Volumes:

Simplify Importance Sampling

• Remove Separation of Direct/Indirect

• Multiple Importance Sampling (MIS)

• Consistent Sampling Domain

Direct vs Indirect

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Multiple Importance Sampling

• Impressive variance reduction

• Requires ability to request pdf arbitrarily

• Can lead to high branching

Mixture Densities

• Simplest combined sampling

• Similar performance to branched MIS

Tagged Objects

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Wavelength Dependence

• Photons have individual wavelengths

• Scattering depends on wavelength

• Color Noise

Color Noise

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Physical Sun and Sky

The Full System

Limitations

Acknowledgments

• State of Utah Center of Excellence

• NSF Grant 03-06151

• Barry M. Goldwater Foundation